Application Examples with Permanent Heating

Application Examples with Permanent Heating 6.4.1 Analytical Determinations... 

The example chosen here to illustrate this type of composite involves a polymeric phase that exhibits rubberlike elasticity. This application is of considerable practical importance since elastomers, particularly those which cannot undergo strain-induced crystallization, are generally compounded with a reinforcing filler. The two most important examples are the addition of carbon black to natural rubber and to some synthetic elastomers and silica to polysiloxane elastomers. The advantages obtained include improved abrasion resistance, tear strength, and tensile strength. Disadvantages include increases in hysteresis (and thus heat buUd-up) and compression set (permanent deformation). 

While most latex house paints fall in the nonreactive class, many applications use a subsequent cross-linking reaction to enhance durability. In a simple example, pendant hydroxyl and carboxyl groups on a polymer chain may not react with each other, while the polymer is suspended as a latex. But when the film is dried and heated, esterification can take place. It may be possible to wash off a fresh film with soap and water, but not one that has aged and become cross-linked. The advantages in an exterior house paint are obvious because cleaning np is easy but permanence (water resistance) inCTeases with time. 

---